TREATMENT OF FISH-CULTURAI^ WATERS FOR REMOVAL OF ALG^. 



877 



during which the remedy is to act. With flowing water the case is more com- 

 pHcated, owing to the necessity of providing a continuing and uniform inflow 

 of the copper sulphate solution adjusted to or varying with the water flow. 

 To do this a convenient method is to dissolve the sulphate in water and allow 

 the solution to flow into the water that is to be treated. The requisites to 

 this operation require some special discussion. 



The strength of the admixture (otherwise termed the dilution) in the pond 

 or stream will depend upon four factors — (i) volume of the water flow that is 

 to be treated; (2) volume of the solution of copper sulphate that is to flow into 



Fig- 1- Fig. 2. 



Note. — In each figure .4 is the siphon, D the frame, and C the container. The form of the frame 

 is of course not essential, and should be adapted to the container. The illustrations show the glass 

 tubing of much larger size than is necessary or practicable in small siphons. Small tubing is preferable. 



it ; (3) rate of flow of the solution ; and (4) quantity of salt dissolved in the solu- 

 tion. The first factor is fixed and must be ascertained. The other three may 

 be varied as convenient to produce the desired strength of admixture. Any 

 two of these three being fixed, the desired result may be obtained by varying 

 the other one. The delivery of the solution at an unvarying rate into the water 

 flow is perhaps the greatest difficulty and is not to be accomplished by any of 

 the ordinary means of delivering liquids from containers. 



If a pipe or tube taps a reservoir containing the solution the head is con- 

 stantly changing as the level of the solution in the reservoir is lowered. The flow 



